The invention relates to a cell having a wound type power generating element in which strip positive and negative electrodes are wound with a strip separator therebetween.
FIG. 9 shows a configuration example of a non-aqueous electrolyte secondary cell having a wound type power generating element 1 of an elliptic cylindrical shape. The power generating element 1 is configured by winding strip negative and positive electrodes 1a and 1b with a strip separator 1c therebetween into an elliptic cylindrical shape. The negative and positive electrodes 1a and 1b are wound with being slightly shifted in the vertical direction from each other, so that only upper edge portions of the negative electrode 1a protrude from the upper end of the power generating element 1 and only lower edge portions of the positive electrode 1b protrude from the lower end. In this case, the active material is not applied to the upper edge portions of the negative electrode 1a, and to the lower edge portions of the positive electrode 1b, thereby allowing metal foils of the negative and positive electrodes 1a and 1b to be respectively exposed in the upper and lower ends of the power generating element 1. The wound separator 1c has a width at which the portion where the negative and positive electrodes 1a and 1b overlap with each other is surely covered and the upper and lower edge portions are not covered.
In such a non-aqueous electrolyte secondary cell, conventionally, a negative collector 2 such as shown in FIG. 10 is disposed on the upper end portion of the power generating element 1 so as to perform current collection on the negative electrode 1a. The negative collector 2 consists of a copper plate and is configured so that a collector portion 2a is formed above one side with respect to the center of the upper end portion of the power generating element 1. A flat platelike terminal connector 2b is drawn out from the collector portion 2a and placed above one semicircular area of the upper end portion of the power generating element 1. In the collector portion 2a, the copper plate is repeatedly bent into a bellow-like shape so as to form press holds 2c which upward protrude, and press insertions 2e which downward protrude. In each of the press holds 2c, the copper plate is bent back at the apex so that two vertical copper plate portions are opposed via a small gap therebetween. In each of the press insertions 2e, the copper plate is bent back at the bottom so that the gap between two inclined copper plate portions is gradually increased to form a V-like section shape.
In the negative collector 2, as shown in FIG. 11, plural edge portions of the negative electrode 1a protruding in the upper end of the power generating element 1 are pressingly held in bundle in each of the press holds 2c of the collector portion 2a and then connected and fixed by crimping and ultrasonic welding. In this case, the collector portion 2a is pressed down from the upper side to the upper end portion of the power generating element 1, thereby pressingly inserting the downward-protruding tip ends of the press insertions 2e into gaps between the upper edge portions of the negative electrode 1a. As a result, the upper edge portions of the negative electrode 1a are distributed by the inclined faces on the both sides of the V-like section shape, and then guided into the gaps of the press holds 2c. 
A positive collector 3 such as shown in FIG. 12 is disposed on the lower end portion of the power generating element 1 so as to perform current collection on the positive electrode 1b. The positive collector 3 is structured in the same manner as the negative collector 2, and has a collector portion 3a. However, the positive collector consists of an aluminum plate in place of a copper plate. In the positive collector 3, edge portions of the positive electrode 1b protruding in the lower end of the power generating element 1 are pressingly held in each of press holds 3c of the collector portion 3a and then connected and fixed by crimping and ultrasonic welding. In this case, similarly, the edge portions of the positive electrode 1b are distributedly guided by press insertions 3e into the gaps of the press holds 3c. In this example, however, a terminal connector 3b is drawn out above the upper end portion of the power generating element 1. In the case where the positive terminal 5 is to protrude from a lower portion of the power generating element 1, also the terminal connector 3b is disposed below the lower end portion of the power generating element 1.
For the sake of simplicity, in the figures, the negative electrode 1a, the positive electrode 1b, and the like of the power generating element 1 are shown so as to be wound coarsely or with a reduced number of turns. In an actual case, they are wound very closely or with a large number of turns, so that many edge portions of the negative and positive electrodes 1a and 1b are pressingly held in the gaps of the press holds 2c and 3c of the collector portions 2a and 3a and then connected and fixed. In some case, the collector portions 2a and 3a of the negative and positive collectors 2 and 3 are disposed not only in one side with respect to the center of the power generating element 1, but also above and below the both sides with respect to the center, thereby improving the current collecting efficiency.
In the negative and positive electrodes 1a and 1b of the power generating element 1, however, very thin metal foils of copper, aluminum, or the like are exposed in the upper and lower edge portions. When the tip ends of the press insertions 2e and 3e of the collector portions 2a and 3a are actually pressingly inserted between the edge portions of the negative and positive electrodes 1a and 1b, therefore, the tip ends catch the inclined faces on the both sides of the V-like section shape, thereby producing a problem in that the edge portions cannot be smoothly guided into the gaps of the press holds 2c and 3c. 
Since the press insertions 2e and 3e are disposed in the collector portions 2a and 3a, the tip ends of the press insertions 2e and 3e are pushed into the power generating element 1. Therefore, there arise further problems in that the tip ends may make contact with the positive or negative electrode 1b or 1a which is not subjected to current collection, to cause a short circuit, and that the application area of the active material is narrowed and hence the cell capacity is reduced. When the negative electrode 1a is to be connected and fixed to the press holds 2c of the collector portion 2a, for example, the upper end of the positive electrode 1b which is placed with being downward shifted approaches the tip ends of the press insertions 2e as shown in FIG. 13. Therefore, there arises a possibility that the upper end makes contact with the tip end so as to cause a short circuit. In order to prevent such a short circuit from occurring, the amount of shift in each of the negative and positive electrodes 1a and 1b may be increased. However, this causes the area where the active material is not applied, to be widened. Consequently, the application area is reduced by an area corresponding to the widened area, thereby reducing the cell capacity.
The problem that the edge portions of the negative and positive electrodes 1a and 1b cannot be smoothly inserted into the gaps of the press holds 2c and 3c may be solved by employing the following configuration. Comb-like jigs which are made of a material of a low coefficient of friction and an excellent sliding property are prepared so as to have elongated V-like teeth in which the tip end is smaller in angle than the press insertions 2e and 3e. The jigs are pressed into the upper and lower end portions of the power generating element 1 so that the upper and lower edge portions of the negative and positive electrodes 1a and 1b are previously distributed to positions respectively corresponding to the gaps of the press holds 2c and 3c. Thereafter, the collector portions 2a and 3a of the negative and positive collectors 2 and 3 are inserted thereinto. However, this countermeasure also cannot solve the problems that the tip ends of the press insertions 2e and 3e may cause a short circuit, and that the application area of the active material is narrowed.
The invention has been conducted in view of such circumstances. It is an object of the invention to provide a cell in which a press hold is directly disposed in a flat metal plate, so that a short circuit with an electrode is prevented from occurring and the application area of the active material can be widened.
The cell of the invention of claim 1 is characterized in that a collector portion of each of collectors comprises: plural press holds in each of which two metal plate portions are projected to be opposed via a gap that opens on a side of a basal portion, by bending back a substantially vertical metal plate at an apex; and flat plate portions which are formed by a flat metal plate portion and through which adjacent ones of the press holds are coupled to each other on the side of the basal portion, the collector portions are respectively placed on ends of a winding axis of a wound type power generating element, with respectively directing the basal portions to the ends, the power generating element being configured by winding strip positive and negative electrodes with a strip separator therebetween with being mutually shifted in the winding axis direction, and edge portions of the positive and negative electrodes which protrude in the ends of the winding axis of the power generating element are pressingly held in nearest press holds of the collector portions to be connected and fixed.
According to the invention of claim 1, the plural press holds which connect and fix the edge portions of the corresponding electrode are coupled to one another through the flat plate portions, and hence the portions are not pushed into the power generating element. Consequently, the electrode which is not connected and fixed by the press holds is prevented from making contact with the collector portion to cause a short circuit. This allows the amount of shift in winding of the positive and negative electrodes, to be reduced. As a result, the area to which the active material is applied can be widened so as to increase the cell capacity.
The cell of the invention of claim 2 is characterized in that the edge portions of the electrodes are inserted between the two metal plate portions of the corresponding press hold of the collector portions, and then connected and fixed to the two metal plate portions by crimping and ultrasonic welding.
According to the invention of claim 2, the edge portions of the electrodes can be surely connected and fixed to the press holds of the collector portions by crimping and ultrasonic welding.
The cell of the invention of claim 3 is characterized in that, in the cell of claim 1, a window is formed in a part of one of the metal plate portions of each of the press holds of the collector portions of the collectors, the window communicating with the gap between the one metal plate portion and the other metal plate portion.
According to the invention of claim 3, the window is formed in a part of one of the metal plate portions of each press hold, and hence the plural electrode edge portions which are pressingly held in the press hold can be surely welded together so as to be connected and fixed, by welding which is performed through the window. The edge portions of the electrodes are exposed to one side through the window. Therefore, welding is not restricted to that based on vibration, such as ultrasonic welding, and may be performed by directly applying heat, as in the case of laser welding.
The cell of the invention of claim 4 is characterized in that the edge portions of the electrodes of the cell of claim 3 are connected and fixed by inserting the edge portions between the two metal plate portions of the corresponding press hold of the collector portions and then crimping the metal plate portions, and also by ultrasonic welding of the window of the one metal plate portion and the other metal plate portion, and a part of the one metal plate portion other than the window and the other metal plate portion.
According to the invention of claim 4, the plural electrode edge portions which are pressingly held in the press hold can be surely held between the part of the one metal plate portion other than the window and the other metal plate portion, by crimping and ultrasonic welding in the same manner as the prior art. Between the one metal plate portion and the other metal plate portion, the plural electrode edge portions are directly ultrasonic welded, and hence surely welded together to be firmly connected and fixed.
The cell of the invention of claim 5 is a cell comprising: a power generating element in which positive and negative electrode plates are wound or laminated with a separator therebetween and an edge portion of one of the electrode plates protrude from an edge portion of another one of the electrode plates; and collectors respectively connected to the edge portions, and characterized in that each of the collectors is formed by bending a metal plate to have plural groove portions which are used for pressingly holding and bonding the edge portion of either of the electrode plates, and a reduced thickness portion is formed in a part of each of the groove portions.
According to the invention of claim 5, the reduced thickness portion is formed in a part of each of the metal plates which is used for pressingly holding edge portions of the corresponding electrode plate. Therefore, the plural electrode edge portions which are pressingly held in the press hold can be surely melted and welded so as to be connected and fixed by welding which is performed through the reduced thickness portion. Both ends of the electrode edge portions are pressingly held by the press holds. Even when a certain external force is applied to the edge portions during ultrasonic welding or after the production of the cell, therefore, the electrode is not broken. As a result, it is possible to attain excellent environmental resistant properties.
The cell of the invention of claim 6 is characterized in that each of the collectors of the cell of claim 5 is formed by a plate member of a thickness of 0.5 to 2 mm and the reduced thickness portion has a thickness which is 10% to 80% of the thickness of the collector.
When the thickness of the reduced thickness portion is adjusted in the range specified in claim 6, welding is not restricted to that based on vibration, such as ultrasonic welding, and can be performed by applying heat through the reduced thickness portion by means of laser welding or the like.